Safety-envelope



UNITED STATES PATENT OFFICE.

W. S. STETSON, OF BALTIMORE, MARYLAND.

SAFETY-ENVELOPE.

Specification forming part of Letters Patent No. 25,590, dated September 27, 1859.

To all whom it may concern Be it known that I, W. S. STETsoN, of Baltimore, in the county of Baltimore and State Maryland, have invented an Improvement in Safety-Envelopes; and I do hereby declare that the following is a full, clear, and exact description of the principle or character which dis- -tinguishes it from all other things before known, and of the usual manner of making, modifying, and using the same.

My invention consists in a mode of preventing the opening of sealed envelopes by the application of moisture, described as follows:

It is well known that envelopes which are sealed by the moistening of some adhesive material applied to them are readily opened by the application of moisture over the sealed part, and this is usually accomplished by laying upon that part a moistened cloth or paper. To prevent the opening of sealed envelopes in this way, I water-proof that part of the envelope which is to be covered with adhesive material, and apply this material to the surface of the waterproofing material. The envelope is sealed by the usual modes of moistening, andcannot be unsealed by the external application of moisture, as it will not penetrate the waterproofing material through to the adhesive material. Varnish of shellac dissolved in alcohol answers well for the waterproofing material, though many others may be used with success. The adhesive material may be WV. S. STETSON.

Witnesses:

SAML. L. K NG, DAVID KNOX. 

